A Synergistic Effect in a Composite Cathode Consisting of Spinel and Layered Structures To Increase the Electrochemical Performance for Li-Ion Batteries

摘要

In this work, a composite consisting of layered Li[Li0.2Ni0.12 Mn0.56Co0.12]O-2 (LNMC) and spinel Li[Ni0.5Mn1.5]O-4. (LNMO) was synthesized by a modified Pechini method. Extensive analysis was carried out to investigate the synergistic effect between the layered oxide and spinels in the composite by comparing its properties with baseline individual compounds, as well as a physical mixture of LMNC and LNMO. Comparing to the LNMC, the compsoite cathode exhibited a similar initial capacity of similar to 250 mA.h/g at 0.1 C, but a much higher first-cycle effeciency, better cyclability and rate capability, attributed to the presence of spinel. The synertistic effect of integrated spinel on the microstructure, crystal strucutre, Mn oxidation states, and Li+/Ni2+ disordering of the composite was studied by X-ray absorption near edge structure (XANES), electron microscopy, and X-ray diffraction (XRD). The presence of a spinel component in the composite cathode is the origin for the improvement of cyclability and rate capability, largely due to a lower Li+/Ni2+ disordering, milder redox reaction of manganese ions, and suppressed converting reaction to form LixMn2O4-like spinel.